1. Field of the Invention
The present invention relates to an apparatus and method for removing a moire pattern, and more particularly, to an apparatus and method for removing a moire pattern from a digital image of a digital imaging device by means of low-pass filtering.
2. Description of the Related Art
A digital imaging device generally photographs an object using an image pick-up device which has a grid structure. A charge-coupled device (CCD) is a typical image pick-up device used as a digital imaging device. A CCD is an image sensor that projects an image of an object onto a particular solid-state device by use of an optical system and electrically scans the projected image to convert light signals into electric signals.
Since a digital imaging method using an image pick-up device enables an image to be obtained as soon as an object is photographed and the photographed image is easy to store, it is widely used in personal cameras, cameras mounted in mobile phones, and the like.
However, unlike an analog imaging device such as a film camera, a digital imaging device can have a moire pattern due to the grid structure of an image sensor. A moire pattern is an undesirable irregular image, which is caused by interference between high frequency components of a repeated pattern of an object to be photographed in a region around a spatial frequency of an image sensor.
Conventionally, a method using an optical low-pass filter (OLPF), that is, a birefringent device, is used to remove a moire pattern. In this method, incident light is divided into more than two light beams with different refraction angles by using the OLPF and then the light beams are focused on an image sensor.
However, since an additional birefringent device is required, the size of an optical system increases. In particular, filtering is always performed even when there is no moire pattern generated so that the sharpness of an image can deteriorate.
Recently, although a method of processing image data in a digitized manner in an image processing chip has been suggested in order to remove a moire pattern, this method can reduce the overall performance of the digital imaging device due to the additional image processing procedure.